NPR新闻：Trump Says Tariffs Are Needed To Protect Vital Industries, But Are They?

When President Trump announced tariffs on steel and aluminum imports earlier this month, he cited concerns about national security. Trump said that for the defense of the country it's CRItical that those two domestic industries are strong. NPR's Jim Zarroli examines that claim.

JIM ZARROLI, BYLINE: Trump said at a press conference that the slow erosion of steel jobs in the United States isn't just an economic disaster - it's also a security disaster.

(SOUNDBITE OF PRESS CONFERENCE)

PRESIDENT Donald Trump: We want to build our ships. We want to build our planes. We want to build our military equipment with steel, with aluminum from our country.

ZARROLI: When the U.S. imposes tariffs, it usually justifies them by saying the manufacturers are being hurt by unfair foreign trade practices. This time Trump invoked the rarely used Section 232 of the Trade Expansion Act of 1962. Nicholas Lardy is a senior fellow at the Peterson Institute for International Economics. He says the law allows the president to slap tariffs on products that are deemed necessary for defense.

NICHOLAS LARDY: One way of doing that is to put on a tariff which makes imported goods more expensive and makes it more likely that domestic firms will be able to continue production.

ZARROLI: What makes the law so attractive for the administration is that it allows the president to act quickly. He doesn't have to spend months or even years building up a case against U.S. trading partners, the way it usually works with tariffs. Because Section 232 is hardly ever used, the impact of the tariffs is unclear. Former Pentagon official Andrew Hunter notes that the U.S. already gives preference to domestic suppliers whenever possible.

ANDREW HUNTER: And a lot of that's driven by a pretty simple sentiment, which is when people give their tax dollars to support the national defense, they hope that those tax dollars are being used in a way that also further supports the economy.

ZARROLI: But the Defense Department needs to buy a tremendous number of products for its tanks and ships and military gear, and there are simply a lot of things the U.S. doesn't produce. Trump may want to see more aluminum manufacturing, for example. But to make aluminum you need bauxite, and it's hardly mined in the U.S. Hunter, who's with the Center for Strategic and International Studies, also points out that global supply chains are incredibly complex.

HUNTER: Almost any item that you could look at and it says made in the USA on it, frequently there is some content in it that comes from overseas.

ZARROLI: Requiring the military to buy too many of the products it needs domestically, he says, would put a huge strain on the Pentagon. Nicholas Lardy of the Peterson Institute also points out that the tariffs are probably not necessary - take steel, for instance.

LARDY: The industry is not in decline in terms of output. So arguing that we need to put on tariffs now to preserve a steel industry that is essential to national security I think is a bit of a stretch.

ZARROLI: And there's another issue. Modern militaries use an enormous number of products of all kinds. Once countries begin to declare certain industries off limits for security reasons, trade could at least in theory grind to a halt. By imposing tariffs, the administration has opened the door to retaliation by other countries, and that could pose as many problems as it solves. Jim Zarroli, NPR News, New York.